TGFB1 and leukemia: Although TGF-β is proposed to be a potent negative regulator of hematopoiesis (Fortunel et al., 2000; Fortunel et al., 2003) and the loss of TGF-β signaling is reported in several leukemias (Le Bousse-Kerdiles et al., 1996; DeCoteau et al., 1997; Jakubowiak et al., 2000; Imai et al., 2001; Wolfraim et al., 2004), the disruption of TGF-β signaling alone is not sufficient to induce leukemia (Datto et al., 1999, Yang et al., 1999; Larsson et al., 2003).